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Title: The Impact of Updated Zr Neutron-capture Cross Sections and New Asymptotic Giant Branch Models on our Understanding of the s process and the origin of stardust

We present model predictions for the Zr isotopic ratios produced by slow neutron captures in C-rich asymptotic giant branch (AGB) stars of masses 1.25-4 M-circle dot and metallicities Z = 0.01-0.03, and compare them to data from single meteoritic stardust silicon carbide (SiC) and high-density graphite grains that condensed in the outflows of these stars. We compare predictions produced using the Zr neutron-capture cross sections from Bao et al. and from n_TOF experiments at CERN, and present a new evaluation for the neutron-capture cross section of the unstable isotope Zr-95, the branching point leading to the production of Zr-96. The new cross sections generally present an improved match with the observational data, except for the Zr-92/Zr-94 ratios, which are on average still substantially higher than predicted. The Zr-96/Zr-94 ratios can be explained using our range of initial stellar masses, with the most Zr-96-depleted grains originating from AGB stars of masses 1.8-3 M-circle dot and the others from either lower or higher masses. The Zr-90,Zr-91/Zr-94 variations measured in the grains are well reproduced by the range of stellar metallicities considered here, which is the same needed to cover the Si composition of the grains produced by the chemical evolution of themore » Galaxy. The Zr-92/Zr-94 versus Si-29/Si-28 positive correlation observed in the available data suggests that stellar metallicity rather than rotation plays the major role in covering the Zr-90,Zr-91,Zr-92/Zr-94 spread« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Monash Univ., Melbourne, VIC (Australia)
  2. Istituto Nazionale di Fisica Nucleare (INFN), Bari (Italy); Univ. of Ghent (Belgium)
  3. Australian National Univ., Canberra, ACT (Australia)
  4. Istituto Nazionale di Fisica Nucleare (INFN), Trieste (Italy)
  5. Karlsruhe Inst. of Technology (KIT) (Germany)
  6. Univ. of Chicago, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States); Univ. of Chicago, IL (United States). Enrico Fermi Inst.
  7. Argonne National Lab. (ANL), Argonne, IL (United States); Chicago Center for Cosmochemistry, Chicago, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 780; Journal Issue: 1; Journal ID: ISSN 0004-637X
Publisher:
Institute of Physics (IOP)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
National Aeronautic and Space Administration (NASA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1357178

Lugaro, M., Tagliente, Giuseppe, Karakas, Amanda I., Milazzo, Paolo M., Kappeler, Franz, Davis, Andrew M., and Savina, Michael R.. The Impact of Updated Zr Neutron-capture Cross Sections and New Asymptotic Giant Branch Models on our Understanding of the s process and the origin of stardust. United States: N. p., Web. doi:10.1088/0004-637X/780/1/95.
Lugaro, M., Tagliente, Giuseppe, Karakas, Amanda I., Milazzo, Paolo M., Kappeler, Franz, Davis, Andrew M., & Savina, Michael R.. The Impact of Updated Zr Neutron-capture Cross Sections and New Asymptotic Giant Branch Models on our Understanding of the s process and the origin of stardust. United States. doi:10.1088/0004-637X/780/1/95.
Lugaro, M., Tagliente, Giuseppe, Karakas, Amanda I., Milazzo, Paolo M., Kappeler, Franz, Davis, Andrew M., and Savina, Michael R.. 2013. "The Impact of Updated Zr Neutron-capture Cross Sections and New Asymptotic Giant Branch Models on our Understanding of the s process and the origin of stardust". United States. doi:10.1088/0004-637X/780/1/95. https://www.osti.gov/servlets/purl/1357178.
@article{osti_1357178,
title = {The Impact of Updated Zr Neutron-capture Cross Sections and New Asymptotic Giant Branch Models on our Understanding of the s process and the origin of stardust},
author = {Lugaro, M. and Tagliente, Giuseppe and Karakas, Amanda I. and Milazzo, Paolo M. and Kappeler, Franz and Davis, Andrew M. and Savina, Michael R.},
abstractNote = {We present model predictions for the Zr isotopic ratios produced by slow neutron captures in C-rich asymptotic giant branch (AGB) stars of masses 1.25-4 M-circle dot and metallicities Z = 0.01-0.03, and compare them to data from single meteoritic stardust silicon carbide (SiC) and high-density graphite grains that condensed in the outflows of these stars. We compare predictions produced using the Zr neutron-capture cross sections from Bao et al. and from n_TOF experiments at CERN, and present a new evaluation for the neutron-capture cross section of the unstable isotope Zr-95, the branching point leading to the production of Zr-96. The new cross sections generally present an improved match with the observational data, except for the Zr-92/Zr-94 ratios, which are on average still substantially higher than predicted. The Zr-96/Zr-94 ratios can be explained using our range of initial stellar masses, with the most Zr-96-depleted grains originating from AGB stars of masses 1.8-3 M-circle dot and the others from either lower or higher masses. The Zr-90,Zr-91/Zr-94 variations measured in the grains are well reproduced by the range of stellar metallicities considered here, which is the same needed to cover the Si composition of the grains produced by the chemical evolution of the Galaxy. The Zr-92/Zr-94 versus Si-29/Si-28 positive correlation observed in the available data suggests that stellar metallicity rather than rotation plays the major role in covering the Zr-90,Zr-91,Zr-92/Zr-94 spread},
doi = {10.1088/0004-637X/780/1/95},
journal = {Astrophysical Journal},
number = 1,
volume = 780,
place = {United States},
year = {2013},
month = {12}
}